Roger Federer says he may pull out of the French Open if there is too much risk to his knee, and to his Wimbledon prospects, from playing on.
The Swiss beat Dominik Koepfer over three-and-a-half hours late on Saturday in only his sixth match since having double knee surgery.
Federer, 39, is due to play Matteo Berrettini in the last 16 on Monday.
But he said he will decide later on Sunday whether now would be the "perfect time to take a rest".
The 20-time Grand Slam champion lacked fluency and trust in his game before coming through to beat Germany's Koepfer 7-6 (7-5) 6-7 (3-7) 7-6 (7-4) 7-5 at a near-empty Roland Garros.
Eighth seed Federer is playing in only his third tournament since January 2020 and says he is using it to build up fitness for Wimbledon, which starts on his favoured grass surface at the end of June.
"We go through these matches, we analyse them highly and look on what's next," he said.
"We will do the same here on Sunday, because I need to decide if I keep on playing or not. Is it not too much risk at this moment to keep on pushing or is this just a perfect way to just take a rest?"
Italy's ninth seed Berrettini, 25, reached the fourth round at Roland Garros for the first time with a 7-6 (8-6) 6-3 6-4 win over South Korea's Kwon Soon-woo.
After hitting 52 winners against Kwon to continue a fine clay-court season, Madrid runner-up Berrettini will be widely considered the favourite against 2009 champion Federer.